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Interesting Facts about Garden Eels
[Phylum: Chordata] [Class: Actinopterygii] [Order: Anguilliformes] [Family: Congridae (marine eels)]
They may look like plants swaying in the current. But, garden eels belong with a family of slender marine eels that spend a lot of time partially buried in soft substrates on the ocean floor.
This section contains facts and information about garden eels, mostly from the genera Heteroconger and Gorgasia, such as where they live, what they eat, and how they reproduce.
Garden Eel Habitat and Geographical Range
Most of the garden eel species live in the warm waters of tropical and subtropical oceans, especially the Atlantic, Indian, and the Pacific.
They tend to gather in large colonies that sometimes contain hundreds of eels - like swaying noodles in the sand.
The scientific name for garden eels is "Congridae" (conger eel) and the most common genera are "Heteroconger" and "Gorgasia".
But, the slightly weird fish name of garden eel comes from the affinity to a group of eels sticking their heads out of a flat lawn.
Garden eels habitats are particularly common on coral reef slopes and near shallow seagrass beds. They prefer living in "burrows" where there is moderate water movement, yet strong enough to deliver a plentiful supply of food.
Garden Eel Key Features
Even though these small marine eels inhabit sandy and muddy sea floors, it's rare to find them living deeper than fifty (40) metres (150 feet).
The average length of garden eels is about forty (40) centimetres (16 inches), often with small spots, stripes, and other identifiable body markings.
But, the longest of the species is the splendid garden eel (Gorgasia preclara) and fully matured adults can grow to 120 centimetres (4 feet) in total body length.
Here's the thing:
Unlike most marine vertebrates, each garden eel lives a unique kind of burrow-dwelling non-swimming lifestyle, existing in a mostly vertical and alert position inside their individual burrows.
In fact, most of their body remains buried while the head and upper body exit the burrow to pick off food particles in the water column.
Furthermore, they will quickly retreat to the safety of their burrow if any perceived threat gets too close (especially scuba divers).
Interesting Fact: Garden eels use a special mucus secreted from the skin to line the inside of the burrow. It adds strength to the structure and helps to stop it from collapsing if they decide to go outside (e.g. to escape predators or completely abandoned during migration).
What Do Garden Eels Eat?
Garden eels have sizeable, prominent eyes. They use them to spot planktonic organisms and to identify potential predators. Living in large colonies also means there could be "hundreds" of eyes looking for food and watching for danger.
They remain partially inside the burrow even when they hunt for food.
But, the eel needs to face into the water flow to catch these tiny food particles.
So, the typical daily diet can also include different types of zooplankton that drift in the water current.
Pro Tip: If you're keeping garden eels in captivity, they will eat various kinds of prepared aquarium food diets, especially brine shrimp.
Garden Eel Reproduction
The seasonal mating period for garden eels tends to have links with a superabundance of plankton and a marginal increase in water temperature.
Colonies become more active during these breeding periods, and the eels "adjust" their positions in the burrow so they can get closer to each other.
Courtship and Mating
For the most part, the males extend their bodies toward nearby mating females outside of the burrow. If there's no conflict, they often sway together side by side and even have a gentle rub of their bodies.
So, without having to leave the burrows, mating eels can align themselves close enough for the release of sperm and eggs simultaneously into the water for external fertilisation.
Larval Stage (Leptocephalus)
The fertilised eggs become part of the plankton and float with ocean currents for up to several months. The larvae of garden eels (called leptocephali) are transparent and shaped like a tiny leaf.
Despite being dispersed over a large area, the larvae eventually settle in a suitable location, create a burrow, and start to develop into adults.
Interesting Fact: Excessive or improper scuba diving tourism (frequent human presence near colonies of garden eels) can increase their stress levels and cause long-term health issues. The eels often stay hidden for extended periods of time, thus reducing their feeding times and quantities.
Garden Eel Species List
Black Garden Eel (Heteroconger perissodon)
Brown Garden Eel (Heteroconger longissimus)
Freckled Garden Eel (Gorgasia maculata)
Galapagos Garden Eel
Giraffe-spotted Garden Eel (Heteroconger camelopardalis)
Hawaiian Garden Eel (Gorgasia hawaiiensis)
Neighbor Conger (Bathycongrus vicinalis)
Red Sea Garden Eel (Gorgasia sillneri)
Splendid Garden Eel (Gorgasia preclara)
Spotted Garden Eel (Heteroconger hassi)
Taylor's Garden Eel (Heteroconger taylori)
White-barred Garden Eel (Heteroconger pellegrini)
Yellow Garden Eel (Heteroconger luteolus)
Threats and Predators
The main predatory fish species that eat garden eels are groupers, triggerfish, and wrasses. They are also eaten by octopuses and crustaceans that can burrow, especially crabs and lobsters.
Other contributing factors for the decline in a few vulnerable areas include certain types of human behaviour such as, habitat destruction (e.g. coastal development), coral reef destruction, sand mining, and warming seas.
Pro Tip: The IUCN Red List of Threatened Species last assessed most of the garden eel species in 2016 and cites most of them as being of "Least Concern" (LC).